BILE-PIGMENT. 313 



to Heintz*, when this reagent contains a little nitrous acid,) first 

 becomes green, then blue (which, however, can hardly be detected 

 in consequence of its rapid transition into violet,) and red ; after 

 a considerable period the red again passes into a yellow colour; by 

 this time, however, the bile-pigment is entirely changed. On the 

 addition of hydrochloric acid to a potash-solution, the pigment is 

 precipitated with a green tint; this precipitate forms a red solution 

 with nitric acid, and a green solution with the alkalies, and appears 

 to be perfectly identical with the green modification of bile-pigment. 

 The colouring matter contained in fresh bile is coloured green by 

 acids ; as Gmelin found that this coloration did not take place 

 without the free access of oxygen, it is highly probable that most 

 of these changes of colour are dependent on a gradual oxidation. 

 Chlorine gas acts on this pigment in the same manner as nitric 

 acid, but rather more rapidly ; large quantities of chlorine com- 

 pletely bleach the pigment, and precipitate it in a white flocculent 

 deposit. 



This brown pigment has a strong tendency to combine with 

 bases, not merely with alkalies, but also with metallic oxides and 

 alkaline earths. It forms insoluble compounds with the alkaline 

 earths a circumstance which has often led to the idea that this 

 substance is insoluble. 



The green pigment, the biliverdin of Berzelius, is a dark green 

 amorphous substance, devoid of taste and smell, insoluble in water, 

 slightly soluble in alcohol, but dissolving in ether with a red 

 colour ; it dissolves in fats, hydrochloric acid, and sulphuric acid with 

 a green colour, and in acetic acid and the alkalies with a yellowish 

 red tint. On exposure to heat, this body undergoes decomposition 

 without fusing, and without giving off any appreciable quantity of 

 ammonia, leaving a little charcoal. Berzelius regards this sub- 

 stance as perfectly identical with the chlorophyll of leaves, and 

 believes that he has found all three modifications of this substance 

 in different specimens of bile. This green pigment no longer 

 undergoes changes of colour on the addition of nitric acid, although 

 we occasionally meet with green bile-pigment still possessing this 

 property. On treating bile-pigment with alkalies or acids, its 

 properties are usually at once changed, partly on account of its 

 entering into various combinations with these substances, and 

 partly from the extreme facility with which it becomes decomposed. 



Hence it is that the statements regarding the properties of this 

 substance present such striking differences, as may be seen by a 

 * Mtiller's Arch. 1840, S. 399-405. 



